1. Field of the Invention
The technical field relates to a semiconductor device.
2. Description of the Related Art
Patent Document 1 discloses a semiconductor device including a transistor.
Paragraph 0012 in Patent Document 1 discloses the following: “it is said that a substance containing a hydrogen element is an element which prevents an oxide semiconductor layer from being highly purified so that the oxide semiconductor layer is not close to an i-type oxide semiconductor layer because a hydrogen element has two factors of inducing carriers”.
Paragraph 0013 in Patent Document 1 discloses the following: “as a substance containing a hydrogen element, for example, hydrogen, moisture, hydroxide, hydride, and the like can be given”.
Patent Document 1 also discloses that, when a substance containing a hydrogen element is contained in an oxide semiconductor layer of a transistor, the threshold voltage of the transistor shifts in a negative direction.